Conventionally, a flush toilet bowl that is washed by flush water that is supplied from a flush water source may include a rim nozzle and a rim water spout part. A rim nozzle spouts flush water from a flush water source to a rim water spout part. A rim water spout part is provided on a rim part that is formed on an upper edge of a waste receiving surface that receives waste, and includes a rim water guide channel and a rim water spout port.
A rim water guide channel is formed inside a rim part, is formed in accordance with a shape of the rim part, and guides flush water that is spouted from a rim nozzle. Furthermore, a rim water guide channel may be formed into, for example, a longitudinally long shape in cross section, for example, in such a manner that a rim part is joined to a waste receiving surface (see, for example, Japanese Patent Application Publication No. 2014-034868). A rim water spout part is formed so as to be continuous with a rim water guide channel, is an exit opening for flush water, and spouts flush water to a waste receiving surface.
In such a flush toilet bowl, for example, abnormal noise such as explosive noise of air or mixing noise of air may be generated at a time of spout of flush water from a rim water spout part (rim water spout port). Accordingly, for example, a flush toilet bowl has been known where a plurality of small holes is formed on a rim nozzle, a space part that is defined by a wall that includes an inner wall where flush water that is spouted from the plurality of small holes on the rim nozzle collides therewith is formed on a rim water guide channel, and flush water from the plurality of small holes collides with the inner wall to fractionize air finely and thereby suppress abnormal noise that is caused by air (see, for example, Japanese Patent Application Publication No. 2008-303616).
Meanwhile, for a conventional flush toilet bowl as described above, it is possible to consider that a rim water spout port is arranged on a rim part in a region on a front side (front side region) with respect to a half of a waste receiving surface in order to cause a user to be difficult to view the rim water spout port, that is, in order to improve a design of a toilet, or in order to improve a washability of flush water on a waste receiving surface.
However, as a rim water spout port is arranged in a front side region of a waste receiving surface, a problem occurs in that a rim water guide channel is long and thereby an amount of air in the rim water guide channel increases so that abnormal noise that is caused by air is readily generated. That is, a conventional flush toilet bowl as described above has room for improvement in quietness thereof.